Pressure switch with diaphragm formed of flexible compressible material containing discrete electrically conductive particles which make and break the circuit

ABSTRACT

A fluid pressure operated switch comprises an electrically conductive body having a passage therethrough, a diaphragm engaging a shoulder on the body around the passage and lying across the latter, and a contact plate spring biassed into engagement with the diaphragm. The diaphragm is formed of a flexible, compressible material which becomes electrically conductive when compressed. The pressure applied by the spring acts on a portion of the diaphragm lying against the shoulder and is normally sufficient to render that portion electrically conductive so that the contact plate is normally electrically connected with the body. When a sufficient pressure exists in the passage, the pressure applied by the spring on the said portion of the diaphragm is reduced to an extent such that the diaphragm is no longer electrically conductive and the contact plate is electrically isolated from the body.

United States Patent 1191 Heap 1451 Feb. 19, 1974 [75] Inventor:

[73] Assignee: The Lucas Electrical Company, Limited, Birmingham,England 22 Filed: Feb. 5, 1973 21 Appl. No.: 329,346

Alec John Heap, Burnley, England [30] Foreign Application Priority DataFeb. 5, 1972 Great Britain 5476/72 [52] US. Cl. 200/83 B, 200/83 N,338/42 [51] Int. Cl. H0lh 35/34, "016 9/06 [58] Field of Search....200/83 N, 83 B, 83 R, 83 V; 338/36, 42, 99

[56] References Cited UNITED STATES PATENTS 2,474,662 6/1949 Fuller338/42 2,752,558 6/1956 Kane 338/42 X 3,394,345 7/1968 Thomas 200/83 V X3,455,165 7/1969 Huet 338/42 X 3,509,296 4/1970 Harshman et al 338/99 X3,573,725 4/1971 Shellhause 200/83 B X FOREIGN PATENTS OR APPLICATIONS1,177,677 7/1957 France 338/42 OTHER PUBLICATIONS IBM TechnicalDisclosure, Vol. 6, No. 5, p. 47; October, 1963; Pneumatic to ElectricTransducer by Meier.

Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A.Vanderhye Attorney, Agent, or Firm-I-Iolman and Stern [5 7] ABSTRACT Afluid pressure operated switch comprises an electrically conductive bodyhaving a passage therethrough, a diaphragm engaging a shoulder on thebody around the passage and lying across the latter, and a contact platespring biassed into engagement with the diaphragm. The diaphragm isformed of a flexible, compressible material which becomes electricallyconductive when compressed. The pressure applied by the spring acts on aportion of the diaphragm lying against the shoulder and is normallysufficient to render that portion electrically conductive so that thecontact plate is normally electrically connected with the body. When asufficient pressure exists in the passage, the pressure applied by thespring on the said portion of the diaphragm is reduced to an extent suchthat the diaphragm is no longer electrically conductive and the contactplate is electrically isolated from the body.

5 Claims, 1 Drawing Figure 1 PRESSURE SWITCH WITH DIAPHRAGM FORMED OFFLEXIBLE COMPRESSIBLE MATERIAL CONTAINING DISCRETE ELECTRICALLYCONDUCTIVE PARTICLES WHICH MAKE AND BREAK THE CIRCUIT This inventionrelates to a fluid pressure operated switch.

A fluid pressure operated switch in accordance with the inventioncomprises a body having a passage therethrough and at least a contactportion which is of conductive material, a diaphragm extending acrosssaid passage and formed of a flexible compressible material containingdiscrete particles of electrically conductive material which are broughtinto contact with one another to establish conductive paths through thematerial when the material is compressed, a contact member spring biasedinto engagement with said diaphragm so as to compress a portion of saiddiaphragm between the contact member and the contact portion of thebody, the arrangement being such that the application of sufficientfluid pressure to said passage to overcome spring bias on the contactmember deforms the diaphragm so that the portion thereof which iscompressed between the contact member and the contact portion of thebody is disengaged from the contact member so as to break the electricalconnection between the contact member and the contact portion of thebody.

An example of the invention is shown in the accompanying drawing whichis a longitudinal cross-section through a switch according to thepresent invention.

The switch shown includes a body formed of an electrically conductivematerial, such as aluminium. The body 10 has a passage 11 therethroughwhich terminates at a shoulder 12 defining a contact portion. Mounted onthe body is an insulating cap-shaped member 13 which carries a terminal14 connected to a conductive contact disc 15 through the intermediary ofa spring 16 which urges the contact member 15 towards the open end ofthe passage 11.

Overlying the shoulder 12 on the body 10 is a diaphragm 17 formed of aknown material consisting of discrete particles of a conductive materialin a compressible matrix such that compression of the matrix betweencontact portion of the body and the contact member 15 will cause anelectrical path to be established between said contacts only through thecom pressed portion of the matrix. The contact member 15 is of largerdiameter than the passage 1 1 so that it overlies a portion of theshoulder 12 forming the contact portion of the body. The spring 16 urgesthe contact member into engagement with the diaphragm 17 and compressesa portion of it overlying the contact portion of the body. Thus, whenthere is no pressure applied in the passage 11, a conductive path isestablished between the terminal 14 and the body 10.

The cup-shaped member 13 has a counter-bore at its end which slidablyreceives the contact member 15. The outer end of this counter-bore has aflared mouth 18 so that the diaphragm 17 is free outwardly of thecontact member 15 to be displaced towards the terminal 14. Thus, when asufficient fluid pressure is applied to the passage 11 to overcome thebiasing of the spring 16 the diaphragm 17 is deformed to a shallow cupshaped configuration with the contact member 15 engaging the centreportion of the diaphragm 17 but not the portion thereof overlying theshoulder 12.

It will be appreciated that when there is no pressure applied to thepassage 1 1 the entire force applied to the contact member 15 by thespring 16 is absorbed through a narrow annular portion of the diaphragml2 overlying the contact portion on the body. When the diaphragm isdeformed, however, the force of the spring 16 is taken by the centreportion of the diaphragm, and insufficient pressure is applied to thediaphragm over the contact portion-on the body to compress the diaphragmsufficiently to cause conductive paths to be established through it.

I claim:

1. A fluid pressure operated switch comprising a body having a passagetherein and at least a contact portion which is of conductive material,a diaphragm extending across said passage and formed of a flexiblecompressible material containing discrete particles of electricallyconductive material which are brought into contact with one another toestablish conductive paths through the material when the material iscompressed, a contact member spring-biased into engagement with saiddiaphragm so as to compress a portion of said diaphragm between thecontact member and the contact portion of the body, the arrangementbeing such that the application of sufficient fluid pressure to saidpassage to overcome spring bias on the contact member deforms thediaphragm so that the portion thereof which is compressed between thecontact member and the contact portion of the body is disengaged fromthe contact member so as to break the electrical connection between thecontact member and the contact portion of the body.

2. A switch as claimed in claim 1, wherein the contact portion of thebody is provided by a shoulder therein against which the diaphragmabuts.

3. A switch as claimed in claim 2, wherein the diaphragm is lodgedbetween the shoulder and an electrically insulating hollow member inwhich is disposed the contact member.

4. A switch as claimed in claim 3, wherein the hollow member carries aterminal electrically connected with the contact member via the springwhich is lodged in the hollow member.

5. A switch as claimed in claim 3, wherein a portion of the hollowmember surrounding the contact member is defined by a flared mouth whichengages the diaphragm.

1. A fluid pressure operated switch comprising a body having a passagetherein and at least a contact portion which is of conductive material,a diaphragm extending across said passage and formed of a flexiblecompressible material containing discrete particles of electricallyconductive material which are brought into contact with one another toestablish conductive paths through the material when the material iscompressed, a contact member spring-biased into engagement with saiddiaphragm so as to compress a portion of said diaphragm between thecontact member and the contact portion of the body, the arrangementbeing such that the application of sufficient fluid pressure to saidpassage to overcome spring bias on the contact member deforms thediaphragm so that the portion thereof which is compressed between thecontact member and the contact portion of the body is disengaged fromthe contact member so as to break the electrical connection between thecontact member and the contact portion of the body.
 2. A switch asclaimed in claim 1, wherein the contact portion of the body is providedby a shoulder therein against which the diaphragm abuts.
 3. A switch asclaimed in claim 2, wherein the diaphragm is lodged between the shoulderand an electrically insulating hollow member in which is disposed thecontact member.
 4. A switch as claimed in claim 3, wherein the hollowmember carries a terminal electrically connected with the contact membervia the spring which is lodged in the hollow member.
 5. A switch asclaimed in claim 3, wherein a portion of the hollow member surroundingthe contact member is defined by a flared mouth which engages thediaphragm.